The solitude and dreamy isolation of private islands are part of their allure. But that isolation also often means that these dream homes are not connected to the mainland electricity grid. And in some cases that can be a significant cost and a big problem, especially for the residents that need to keep the lights on.
If a private island is close enough to the mainland, a submarine cable can be put down and electricity will flow across the water to the island. But if an island is at a reasonable distance, and connecting it to the power grid is too expensive, or even impossible, solar/wind/water/backup diesel powered generators provide an alternative that can make for a pretty clean and green solution.
At Trinity Island, the energy system consists of three hydroelectric generators, a group of four small wind generators and an array of solar electric panels sited at different locations around the island as determined by optimum availability of resources. This is supplemented by two small pre-existing generators of 5-6kW capacity that have been upgraded and brought into the system to supply a useful amount of energy during circumstances of low water flow at Laig Farm.
A series of inverters continuously monitors the state of charge of the batteries. When they begin to get close to fully charged, a signal is sent to the generators to come on to supplement their output. The surplus energy is then absorbed by a sequence of frequency controlled switches that activate space heaters at community facilities including the community hall, pier centre and churches.
With this in place, energy consumption on the island falls to a minimum in the summer months, but rises during winter – largely because of the increased demand for heating. In the case of a very cloudy day that is not generating any solar or wind energy, backup power is provided by a natural gas combined heat and power (CHP) generator.
The balancing act is made possible by using supercapacitors from New York-based Kilowatt Labs that store energy at rates much higher than lithium batteries, without the degradation in performance that typically occurs as battery cells age. One megawatt-hour of storage provides the Trinity Island power company with the necessary energy to bridge the seasonal gaps.
Despite these challenges, the islands represented a unique opportunity to create a system that could set a global example of transforming to clean energy for other remote communities. This is because, unlike cities that have to pay for their electricity from the public grid, islanders have a strong incentive to cut costs by going independent. To that end, the islanders are supported by a DOE-funded program called the Island Energy Technology Integration Pilot Program (ETIPP) that connects competitively selected island communities with national and regional energy experts to identify optimal energy solutions. In addition to the Island Energy Technologies, the project partners with the National Renewable Energy Laboratory and other leading institutions from across the country.